When a copper wiring is formed by photoetching in course of the manufacturing of a printed wiring board, iron chloride based etchants, copper chloride based etchants, alkaline etchants and the like are used for the etchant. These etchants, however, have a problem called undercut in which copper beneath an etching resist is dissolved. Particularly, in the case of a finer wiring pattern, the undercut should be minimized.
Conventionally, an etchant for suppressing the undercut has been examined. For instance, JP 3387528 B proposes an aqueous solution containing: cupric chloride; hydrochloric acid; a 2-aminobenzothiazole based compound; polyethylene glycol and a polyamine compound.
However, such a conventional etchant is insufficient for suppressing undercut in some cases, and therefore an etchant with an increased effect for suppressing undercut is required.